Phantom use in DSL system

ABSTRACT

Superimposing phantom-mode signals reinforces existing differentially driven DSL downstream signals in a vectored binder of DSLs or reinforces upstream vectored signals in a binder of differentially excited twisted pairs, thus expanding the extra transmission modes of the previous GDSL multi-wire two-sided-excitation invention to the case where coordination can only occur on one-side of the binder. Each pair is treated as a common-mode antenna with respect to earth ground, with some pairs selectively excited at the transformer center tap at the transmit end with respect to a common (earth or chassis) ground reference. Corresponding receivers on other non-excited pairs sense the signals between their center taps and a ground at the opposite ends of the lines to the exciting transmitters. A dual use with hybrid circuits allows the receiving circuit to also have an upstream transmitter and an upstream-sensing receiver on the center tap of the opposite side of an adjacent wire.

CLAIM OF PRIORITY

This application is a divisional of, and claims priority to, theprovisional utility application entitled “PHANTOM USE IN DSL SYSTEM,”filed on May 9, 2005, having an application No. 60/678,977; and thenon-provisional utility application entitled “PHANTOM USE IN DSLSYSTEM,” filed on Nov. 4, 2005, having an application Ser. No.11/267,623.

TECHNICAL FIELD

This invention relates generally to methods, systems and apparatus formanaging digital communications systems.

BRIEF SUMMARY

This invention is a means for superimposing phantom-mode signals toreinforce existing differentially driven DSL downstream signals in avectored binder of DSLs. Alternative embodiments of the presentinvention provide phantom-mode diversity reinforcement of upstreamvectored signals in a binder of differentially excited twisted pairs.The invention essentially expands the extra transmission modes of theprevious GDSL multi-wire two-sided-excitation invention to the casewhere coordination can only occur on one-side of the binder.

Essentially each pair is treated as a common-mode antenna with respectto earth ground, with some pairs selectively excited at the transformercenter tap at the transmit end with respect to a common (earth orchassis) ground reference. Corresponding receivers on other non-excitedpairs sense the signals between their center taps and a ground at theopposite ends of the lines to the exciting transmitters. A dual use withhybrid circuits allows the receiving circuit to also have an upstreamtransmitter and an upstream-sensing receiver on the center tap of theopposite side of an adjacent wire.

In some embodiments of the present invention, a phantom-mode signalcommunication system has a first communication line configured tooperate as a transmission antenna and a second communication lineconfigured to operate as a reception antenna. The phantom-mode signalcommunication system can be implemented so that the first communicationline is a first DSL loop having a center tap at a first end and a centertap at a second end, wherein the first loop first end center tap has anexcitation voltage generator coupled thereto and further wherein thefirst loop second end center tap has an open circuit coupled thereto.The second communication line then can be a second DSL loop having acenter tap at a first end and a center tap at a second end, wherein thesecond loop first end center tap has an open circuit coupled thereto andfurther wherein the second loop second end center tap has an impedanceconnecting the second loop second end center tap to ground. Applicationof the excitation voltage to the first DSL loop first end center tapgenerates a phantom-mode signal that is broadcast to and received by thesecond DSL loop impedance.

Further details and advantages of the invention are provided in thefollowing Detailed Description and the associated Figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be readily understood by the followingdetailed description in conjunction with the accompanying drawings,wherein like reference numerals designate like structural elements, andin which:

FIG. 1 is a schematic block reference model system per the G.997.1standard applicable to ADSL, VDSL and other communication systems inwhich embodiments of the present invention may be used.

FIG. 2 is a schematic diagram illustrating generic, exemplary DSLdeployment.

FIG. 3A is a schematic diagram of a transmission antenna according toone embodiment of the present invention.

FIG. 3B is a schematic diagram of a reception antenna according to oneembodiment of the present invention.

FIG. 3C is a schematic diagram of a transmission pair according to oneembodiment of the present invention.

FIG. 4A is a controller including a phantom-mode signal control unitaccording to one embodiment of the present invention.

FIG. 4B is the DSL optimizer according to one embodiment of the presentinvention.

FIG. 5 is a flow diagram of a method according to one embodiment of thepresent invention.

FIG. 6 is a block diagram of a typical computer system or integratedcircuit system suitable for implementing embodiments of the presentinvention.

DETAILED DESCRIPTION

The following detailed description of the invention will refer to one ormore embodiments of the invention, but is not limited to suchembodiments. Rather, the detailed description is intended only to beillustrative. Those skilled in the art will readily appreciate that thedetailed description given herein with respect to the Figures isprovided for explanatory purposes as the invention extends beyond theselimited embodiments.

Embodiments of the present invention implement use of phantom lines in acommunication system to add data transmission capacity and/or tostrengthen existing communications. The communication system in whichembodiments of the present invention may be used may be an ADSL system,a VDSL system or any other communication system in which the presentinvention is practical, as will be appreciated by those skilled in theart after reading the present disclosure.

As described in more detail below, a phantom-mode signal control unitimplementing one or more embodiments of the present invention can bepart of a controller (for example, in or as a DSL optimizer, dynamicspectrum manager or spectrum management center). The controller and/orphantom-mode signal control unit can be located anywhere. In someembodiments, the controller and/or phantom-mode signal control unitreside in a DSL CO. In other cases they may be operated by a third partylocated outside the CO. Also, they may be operated by the serviceprovider who owns the CO but in a place physically distinct from (andcoupled to) the CO. The structure, programming and other specificfeatures of a controller and/or phantom-mode signal control unit usablein connection with embodiments of the present invention will be apparentto those skilled in the art after reviewing the present disclosure.

A controller, such as a DSL optimizer, dynamic spectrum managementcenter (DSM Center), a “smart” modem and/or computer system can be usedto collect and analyze the operational data and/or performance parametervalues as described in connection with the various embodiments of thepresent invention. The controller and/or other components can be acomputer-implemented device or combination of devices. In someembodiments, the controller is in a location remote from the modems. Inother cases, the controller may be collocated with one of or both of themodems as equipment directly connected to a modem, DSLAM or othercommunication system device, thus creating a “smart” modem. The phrases“coupled to” and “connected to” and the like are used herein to describea connection between two elements and/or components and are intended tomean coupled either directly together, or indirectly, for example viaone or more intervening elements or via a wireless connection, whereappropriate.

Some of the following examples of embodiments of the present inventionwill use vectored ADSL and/or VDSL systems as exemplary communicationssystems. Within these DSL systems, certain conventions, rules,protocols, etc. may be used to describe operation of the exemplary DSLsystem and the information and/or data available from customers (alsoreferred to as “users”) and/or equipment on the system. However, as willbe appreciated by those skilled in the art, embodiments of the presentinvention may be applied to various communications systems, and theinvention is not limited to any particular system.

Various network-management elements are used for management of ADSL andVDSL physical-layer resources, where elements refer to parameters orfunctions within an ADSL or VDSL modem pair, either collectively or atan individual end. A network-management framework consists of one ormore managed nodes, each containing an agent. The managed node could bea router, bridge, switch, modem or other. At least one NMS (NetworkManagement System), which is often called the manager, monitors andcontrols managed nodes and is usually based on a common PC or othercomputer. A network management protocol is used by the manager andagents to exchange management information and data. The unit ofmanagement information is an object. A collection of related objects isdefined as a Management Information Base (MIB).

FIG. 1 shows the reference model system according to the G.997.1standard (G.ploam), which applies to various ADSL and VDSL systems,which is well known to those skilled in the art, and in whichembodiments of the present invention can be implemented. This modelapplies to ADSL and VDSL systems meeting the various standards that mayor may not include splitters, such as ADSL1 (G.992.1), ADSL-Lite(G.992.2), ADSL2 (G.992.3), ADSL2-Lite (G.992.4), ADSL2+ (G.992.5),VDSL1 (G.993.1) and other G.993.x emerging VDSL standards, as well asthe G.991.1 and G.991.2 SHDSL standards, all with and without bonding.These standards, variations thereto, and their use in connection withthe G.997.1 standard are all well known to those skilled in the art.

The G.997.1 standard specifies the physical layer management for ADSLand VDSL transmission systems based on the clear embedded operationchannel (EOC) defined in G.997.1 and use of indicator bits and EOCmessages defined in G.99x standards. Moreover, G.997.1 specifies networkmanagement elements content for configuration, fault and performancemanagement. In performing these functions, the system utilizes a varietyof operational data that are available at and can be collected from anaccess node (AN). The DSL Forum's TR-069 report also lists the MIB andhow it might be accessed. In FIG. 1, customers' terminal equipment 110is coupled to a home network 112, which in turn is coupled to a networktermination unit (NT) 120. In the case of an ADSL system, NT 120includes an ATU-R 122 (for example, a modem, also referred to as atransceiver in some cases, defined by one of the ADSL and/or VDSLstandards) or any other suitable network termination modem, transceiveror other communication unit. The remote device in a VDSL system would bea VTU-R. As will be appreciated by those skilled in the art and asdescribed herein, each modem interacts with the communication system towhich it is connected and may generate operational data as a result ofthe modem's performance in the communication system. NT 120 alsoincludes a management entity (ME) 124. ME 124 can be any suitablehardware device, such as a microprocessor, microcontroller, or circuitstate machine in firmware or hardware, capable of performing as requiredby any applicable standards and/or other criteria. ME 124 collects andstores performance data in its MIB, which is a database of informationmaintained by each ME, and which can be accessed via network managementprotocols such as SNMP (Simple Network Management Protocol), anadministration protocol used to gather information from a network deviceto provide to an administrator console/program or via TL1 commands, TL1being a long-established command language used to program responses andcommands between telecommunication network elements.

Each ATU-R in a system is coupled to an ATU-C in a CO or other upstreamand/or central location. In a VDSL system, each VTU-R in a system iscoupled to a VTU-O in a CO or other upstream and/or central location(for example, any line termination device such as an ONU/LT, DSLAM, RT,etc.). In FIG. 1, ATU-C 142 is located at an access node (AN) 140 in aCO 146. AN 140 may be a DSL system component, such as a DSLAM, ONU/LT,RT or the like, as will be appreciated by those skilled in the art. AnME 144 likewise maintains an MIB of performance data pertaining to ATU-C142. The AN 140 may be coupled to a broadband network 170 or othernetwork, as will be appreciated by those skilled in the art. ATU-R 122and ATU-C 142 are coupled together by a loop 130, which in the case ofADSL (and VDSL) typically is a telephone twisted pair that also carriesother communication services.

Several of the interfaces shown in FIG. 1 can be used for determiningand collecting operational and/or performance data. To the extent theinterfaces in FIG. 1 differ from another ADSL and/or VDSL systeminterface scheme, the systems are well known and the differences areknown and apparent to those skilled in the art. The Q-interface 155provides the interface between the NMS 150 of the operator and ME 144 inAN 140. All the parameters specified in the G.997.1 standard apply atthe Q-interface 155. The near-end parameters supported in ME 144 arederived from ATU-C 142, while the far-end parameters from ATU-R 122 canbe derived by either of two interfaces over the U-interface. Indicatorbits and EOC messages, which are sent using embedded channel 132 and areprovided at the PMD layer, can be used to generate the required ATU-R122 parameters in ME 144. Alternately, the OAM (Operations,Administrations and Management) channel and a suitable protocol can beused to retrieve the parameters from ATU-R 122 when requested by ME 144.Similarly, the far-end parameters from ATU-C 142 can be derived byeither of two interfaces over the U-interface. Indicator bits and EOCmessages, which are provided at the PMD layer, can be used to generatethe required ATU-C 142 parameters in ME 124 of NT 120. Alternately, theOAM channel and a suitable protocol can be used to retrieve theparameters from ATU-C 142 when requested by ME 124.

At the U-interface (which is essentially loop 130), there are twomanagement interfaces, one at ATU-C 142 (the U-C interface 157) and oneat ATU-R 122 (the U-R interface 158). Interface 157 provides ATU-Cnear-end parameters for ATU-R 122 to retrieve over the U-interface 130.Similarly, interface 158 provides ATU-R near-end parameters for ATU-C142 to retrieve over the U-interface 130. The parameters that apply maybe dependent upon the transceiver standard being used (for example,G.992.1 or G.992.2).

The G.997.1 standard specifies an optional OAM communication channelacross the U-interface. If this channel is implemented, ATU-C and ATU-Rpairs may use it for transporting physical layer OAM messages. Thus, thetransceivers 122, 142 of such a system share various operational andperformance data maintained in their respective MIBs.

More information can be found regarding ADSL NMSs in DSL Forum TechnicalReport TR-005, entitled “ADSL Network Element Management” from the ADSLForum, dated March 1998. Also, DSL Forum Technical Report TR-069,entitled “CPE WAN Management Protocol” dated May 2004. Finally, DSLForum Technical Report TR-064, entitled “LAN-Side DSL CPE ConfigurationSpecification” dated May 2004. These documents address differentsituations for CPE side management and the information therein is wellknown to those skilled in the art. More information about VDSL can befound in the ITU standard G.993.1 (sometimes called “VDSL1”) and theemerging ITU standard G.993.2 (sometimes called “VDSL2”), as well asseveral DSL Forum working texts in progress, all of which are known tothose skilled in the art. For example, additional information isavailable in the DSL Forum's Technical Report TR-057 (FormerlyWT-068v5), entitled “VDSL Network Element Management” (February 2003)and Technical Report TR-065, entitled “FS-VDSL EMS to NMS InterfaceFunctional Requirements” (March 2004) as well as in the emergingrevision of ITU standard G.997.1 for VDSL1 and VDSL2 MIB elements, or inthe ATIS North American Draft Dynamic Spectrum Management Report,NIPP-NAI-2005-03 1.

It is less common for lines sharing the same binder to terminate on thesame line card in ADSL, than it is in VDSL. However, the followingdiscussion of xDSL systems may be extended to ADSL because commontermination of same-binder lines might also be done (especially in anewer DSLAM that handles both ADSL and VDSL). In a typical topology of aDSL plant, in which a number of transceiver pairs are operating and/orare available, part of each subscriber loop is collocated with the loopsof other users within a multi-pair binder (or bundle). After thepedestal, very close to the Customer Premises Equipment (CPE), the looptakes the form of a drop wire and exits the bundle. Therefore, thesubscriber loop traverses two different environments. Part of the loopmay be located inside a binder, where the loop is sometimes shieldedfrom external electromagnetic interference, but is subject to crosstalk.After the pedestal, the drop wire is often unaffected by crosstalk whenthis pair is far from other pairs for most of the drop, but transmissioncan also be more significantly impaired by electromagnetic interferencebecause the drop wires are unshielded. Many drops have 2 to 8twisted-pairs within them and in situations of multiple services to ahome or bonding (multiplexing and demultiplexing of a single service) ofthose lines, additional substantial crosstalk can occur between theselines in the drop segment.

A generic, exemplary DSL deployment scenario is shown in FIG. 2. All thesubscriber loops of a total of (L+M) users 291, 292 pass through atleast one common binder. Each user is connected to a Central Office (CO)210, 220 through a dedicated line. However, each subscriber loop may bepassing through different environments and mediums. In FIG. 2, Lcustomers or users 291 are connected to CO 210 using a combination ofoptical fiber 213 and twisted copper pairs 217, which is commonlyreferred to as Fiber to the Cabinet (FTTCab) or Fiber to the Curb.Signals from transceivers 211 in CO 210 have their signals converted byoptical line terminal 212 and optical network terminal 215 in CO 210 andoptical network unit (ONU) 218. Modems 216 in ONU 218 act astransceivers for signals between the ONU 218 and users 291.

Users' lines that co-terminate in locations such as COs 210, 218 and ONU220 (as well as others) may be operated in a coordinated fashion, suchas vectoring. In vectored communication systems (such as vectored ADSLand/or VDSL systems), coordination of signals and processing can beachieved. Downstream vectoring occurs when multiple lines' transmitsignals from a DSLAM or LT are co-generated with a common clock andprocessor. In VDSL systems with such a common clock, the crosstalkbetween users and the useful crosstalk-phantom signals used in thisinvention to increase data rates and/or reliability, occur separatelyfor each tone. Thus each of the downstream tones for many users can beindependently generated by a common vector transmitter. Similarly,upstream vectoring occurs when a common clock and processor are used toco-receive multiple lines' signals. In VDSL systems with such a commonclock, the crosstalk between users and the useful crosstalk-phantomsignals used in this invention to increase data rates and/orreliability, occur separately for each tone. Thus each of the upstreamtones for many users can be independently processed by a common vectorreceiver.

The loops 227 of the remaining M users 292 are copper twisted pairsonly, a scenario referred to as Fiber to the Exchange (FTTEx). Wheneverpossible and economically feasible, FTTCab is preferable to FTTEx, sincethis reduces the length of the copper part of the subscriber loop, andconsequently increases the achievable rates. The existence of FTTCabloops can create problems to FTTEx loops. Moreover, FTTCab is expectedto become an increasingly popular topology in the future. This type oftopology can lead to substantial crosstalk interference and may meanthat the lines of the various users have different data carrying andperformance capabilities due to the specific environment in which theyoperate. The topology can be such that fiber-fed “cabinet” lines andexchange lines can be mixed in the same binder.

As can be seen in FIG. 2, the lines from CO 220 to users 292 sharebinder 222, which is not used by the lines between CO 210 and users 291.Moreover, another binder 240 is common to all the lines to/from CO 210and CO 220 and their respective users 291, 292. In FIG. 2, far endcrosstalk (FEXT) 282 and near end crosstalk (NEXT) 281 are illustratedas affecting at least two of the lines 227 collocated at CO 220.

As will be appreciated by those skilled in the art, at least some of theoperational data and/or parameters described in these documents can beused in connection with embodiments of the present invention. Moreover,at least some of the system descriptions are likewise applicable toembodiments of the present invention. Various types of operational dataand/or information available from a DSL NMS can be found therein; othersmay be known to those skilled in the art.

FIG. 3A illustrates the excitation of a downstream phantom mode, viewingthis mode in the single-sided case as essentially equivalent to a largelong antenna 310. Both wires 312 of the long system carry the phantomcomponent equally, and the two wires 312 could be considered as one(fatter) wire that comprises the antenna 310. FIG. 3B shows the receiveantenna 390 made up of wires 392 that are close enough to receive thesignals from antenna 310, for example where wires 392 share a binderwith wires 312 and presumably are close to the transmit antenna 310 inFIG. 3A.

FIG. 3C redraws each pair of wires 312, 392 as one line 310, 390,respectively, and views both transmit and receive lines as antennas.Because it is possible to separate currents in the transmit and receivedirections with a “hybrid” circuit 340 (or if not perfect, through theuse also of an echo canceller), then the downstream transmit antenna 310of line 1 also can be viewed as an upstream receive antenna for thephantom signal from the transmit antenna 390 of line 2. (It may not bepractical for various reasons to terminate the client/user side of line1 and try to use it to also receive the downstream phantom signals ofline 2 and vice versa). In such cases, the lines can be divided into twogroups, those to be used for downstream transmission (and consequentlyreverse upstream paths' reception) and those for upstream transmissionand consequent downstream reception.

Many communication systems (for example, ADSL and VDSL systems) have amatrix channel H that characterizes a multiple-input-multiple outputchannel. That channel also may be evident in systems using embodimentsof this invention. In such a system, there are U coordinated lines. Eachof the normal differential transfers, as well as the possible phantomtransfers shown in FIGS. 3A-3C, could be measured adaptively. Forpurposes of this disclosure the “connection-side” of a line is the sideof the line on which the hybrid circuit (or any other embodiment of thepresent invention) is used. Therefore, according to some embodiments ofthe present invention, no hybrid for phantoms is used on the other side(“non-connection side”) of that same line. According to theseembodiments, that connection side can be either the LT/CO/DSLAM side orthe CPE side, but not both on the same line. Up to L_(down) phantoms maybe used for downstream transmissions on the LT connection side, leavingthen U-L_(down) phantoms for connection on the CPE side (that is,upstream transmissions), where L_(down)=1, . . . , U-1. It is alwayspossible to change the side that is called the connection side on anyline by switching in or out the hybrid circuits correspondingly. Onceall transfers are measured a larger 2U×2U matrix can be formed thatcontains all possible transfers for all of the possible connection-sideconfigurations. The downstream matrix H_(down) might be structured into4 U×U parts as shown below:

$H_{down} = \begin{bmatrix}{diff} & {LTconnect} \\{CPEconnect} & {phantomcrosstalk}\end{bmatrix}$

The “diff” or differential part always exists and corresponds to thenormal modes of differentially excited transmission and thecorresponding crosstalk. The LT connect columns (the last U columns)correspond to use of the LT as the connection side and so havedownstream transmitters at the LT side. In any of these columns, eachrow entry corresponds to the output from the corresponding phantominput. If this row is in the upper U, then the signal representscrosstalk from a phantom into a differential signal downstream (suchcrosstalk may be useful or detrimental, depending on how it is used).Such crosstalk will be on the order of the balance of the phone line interms of its general magnitude (and intermediate in size to main linetransfers and FEXT signals for the differential-to-differential lines).

The CPE connect rows (lower U rows) represent systems with the CPE asthe connection side and so have downstream receivers at the CPE side.Each row corresponds to one such downstream receiver. The first Uentries in each row correspond to crosstalk from differentially excitedmodes into the phantom receiver corresponding to this row. The last Uentries in any row correspond to signals received from phantomexcitations. At least one row and one column, but no more than U-1 rowsand U-1 columns, need to be eliminated once the connection sides havebeen determined. This elimination allows a total of U phantoms to beused (either upstream or downstream). The lower right U×U matrix of“phantom crosstalk” has no twisting protection on either the transmitantenna or the receive antenna and so could represent substantialcrosstalk terms (depending on line proximities) on the non-diagonalterms. The diagonal terms of this lower right “phantom crosstalk” matrixare all zero because the line cannot transmit in common mode to itselfin the architecture of this invention.

Algorithms, such as ordering algorithms invented by Adaptive Spectrumand Signal Alignment, Inc. of Redwood City, Calif., or others, can beused to assign L_(down) lines to downstream transmission or to an LTconnect set. Numbering the phantom mode possibilities from i=1, . . . ,U, if the i^(th) line is in the CPE connect set, then the i^(th) columnin the LT connect set (the last U columns) is deleted, and the i^(th)row in the CPE connect set (last U rows) is kept. Upon completion ofthis numbering assignment, the matrix H_(down) will be reduced in sizeto an (2U-L_(down))×(U+L_(down)) matrix. Any other techniques addressingor dealing with an H matrix in DSL and other communication systemstypically may be applied to the enlarged H matrix according to thepresent invention, keeping in mind its unusual dimension properties, aswill be appreciated by those skilled in the art.

Similarly there is a matrix H_(up) that also is 2U×2U originally and hasa 4-quadrant structure like H_(down), except that the CPE-connect andLT-connect are reversed in position:

$H_{up} = \begin{bmatrix}{diff} & {CPEconnect} \\{LTconnect} & {phantomcrosstalk}\end{bmatrix}$

When the i^(th) column of H_(down) is eliminated, then the i^(th) row ofH_(up) is correspondingly eliminated. Similarly when the i^(th) row ofH_(down) is kept, then the i^(th) column of H_(up) is correspondinglykept. The result will be a reduced-size H_(up) that is a(U+L_(down))×(2U-L_(down)) matrix. Any other techniques addressing ordealing with an H matrix in DSL and other communication systemstypically may be applied to the enlarged H matrix according to thepresent invention, keeping in mind its unusual dimension properties, aswill be appreciated by those skilled in the art. Any treatment,manipulation, use, etc. of channel matrices applicable to systems suchas those with which the present invention can be used may then beapplied to the H_(down) and H_(up) identified above. Similarly, as willbe appreciated by those skilled in the art, some of these matrices maybe allocated as necessary to downstream or upstream channels to exploitphantom capacity as best as possible.

Some embodiments of this invention recognize that grounding some of theused lines in the binder to earth ground will cause larger crosstalkmodes between the remaining antenna. This effectively corresponds toplacing 0 voltage on the center tap of the exciting connect sidetransformer (even if no differential is used)—the transformeroutput-side winding is best used in this case for the ground. It may bepossible to excite a line on the output transformer side for all phantomvoltages (and to receive on that line side at the CPE connectlocations), but this may create an isolation/safety hazard in practicewhen not a ground. Grounding of lines will be appreciated by one skilledin the art as possibly improving the antenna transfer properties of theother phantom modes.

Also, embodiments of the present invention can operate bi-directionallyso that inter-pair phantom transfers used for downstream can beseparated using a-phantom hybrid circuit for upstream reception acrossthose same lines. A phantom hybrid circuit would be similar in basicstructure to hybrid circuits well known to those skilled in the art andused for separation of downstream and upstream signals on differentialconnections. However, the phantom hybrid would instead connect betweenthe center tap and the selected ground for the phantom source(downstream) and load (upstream) at the VTU-O (or ATU-C) side. Similarlythe phantom hybrid would connect between the center tap and the selectedground for the phantom source (upstream) and load (downstream) at theVTU-R (or ATU-R) side (on another line).

According to one embodiment of the present invention shown in FIG. 4A, aphantom-mode signal control unit 400 may be part of an independententity coupled to a DSL system, such as a controller 410 (for example, adevice functioning as or with a DSL optimizer, DSM server, DSM Center ora dynamic spectrum manager) assisting users and/or one or more systemoperators or providers in operating and, perhaps, optimizing use of thesystem. (A DSL optimizer may also be referred to as a dynamic spectrummanager, Dynamic Spectrum Management Center, DSM Center, SystemMaintenance Center or SMC.) In some embodiments, the controller 410 maybe an ILEC or CLEC operating a number of DSL lines from a CO or otherlocation. As seen from the dashed line 446 in FIG. 4A, the controller410 may be in the CO 146 or may be external and independent of CO 146and any company operating within the system. Moreover, controller 410may be coupled to and/or controlling DSL and/or other communicationlines in multiple COs.

The phantom-mode signal control unit 400 includes a data collection unitidentified as a collecting means 420 and an analysis unit identified asanalyzing means 440. As seen in FIG. 4A, the collecting means 420 may becoupled to NMS 150, ME 144 at AN 140 and/or the MIB 148 maintained by ME144, any or all of which may be part of an ADSL and/or VDSL system forexample. Data also may be collected through the broadband network 170(for example, via the TCP/IP protocol or other protocol or means outsidethe normal internal data communication within a given DSL system). Oneor more of these connections allows the phantom-mode signal control unitto collect operational data from the system. Data may be collected onceor over time. In some cases, the collecting means 420 will collect on aperiodic basis, though it also can collect data on-demand or on anyother non-periodic basis (for example, when a DSLAM or other componentsends data to the state transition control unit), thus allowing thephantom-mode signal control unit 400 to update its information,operation, etc., if desired. Data collected by means 420 is provided tothe analyzing means 440 for analysis and any decision regardingoperation of one or more communication lines being used to transmit datausing phantom-mode signals.

In the exemplary system of FIG. 4A, the analyzing means 440 is coupledto a DSLAM, modem and/or system operating signal generating means 450 inthe controller 410. This signal generator 450 (for example, a computer,processor, IC or system or component of such a device) is configured togenerate and send instruction signals to modems and/or other componentsof the communication system (for example, ADSL and/or VDSL transceiversand/or other equipment, components, etc. in the system). Instructionsmay include assignment of loops to upstream or downstream transmissionor reception status, hybrid device operation or other instructionsregarding acceptable data rates, transmit power levels, coding andlatency requirements, etc. The instructions may be generated after thecontroller 410 determines the availability and suitability ofphantom-mode signal operation on one or more loops in the communicationsystem.

Embodiments of the present invention can utilize a database, library orother collection of data pertaining to the data collected, pastoperation using phantom-mode signals, etc. This collection of referencedata may be stored, for example, as a library 448 in the controller 410of FIG. 4A and used by the analyzing means 440 and/or collecting means420. In some embodiments of the present invention, the phantom-modesignal control unit 400 may be implemented in one or more computers suchas PCs, workstations or the like. The collecting means 420 and analyzingmeans 440 may be software modules, hardware modules (for example, one ormore computers, processors, ICs, etc. or a system or component based onsuch a device) or a combination of both, as will be appreciated by thoseskilled in the art. When working with a large numbers of modems,databases may be introduced and used to manage the volume of datacollected.

Another embodiment of the present invention is shown in FIG. 4B. A DSLoptimizer 465 operates on and/or in connection with a DSLAM 485 or otherDSL system component, either or both of which may be on the premises 495of a telecommunication company (a “telco”). The DSL optimizer 465includes a data module 480, which can collect, assemble, condition,manipulate and supply operational data for and to the DSL optimizer 465.Module 480 can be implemented in one or more computers such as PCs orthe like. Data from module 480 is supplied to a DSM server module 470for analysis (for example, determining the availability of phantom-modesignal operation for given pairs of communication lines, modification ofexisting phantom-mode signal operation, etc.). Information also may beavailable from a library or database 475 that may be related orunrelated to the telco.

An operation selector 490 may be used to implement, modify and/or ceasephantom-mode signal operation. Such decisions may be made by the DSMserver 470 or by any other suitable manner, as will be appreciated bythose skilled in the art. Operational modes selected by selector 490 areimplemented in the DSLAM 485 and/or any other appropriate DSL systemcomponent equipment. Such equipment may be coupled to DSL equipment suchas customer premises equipment 499. In the case of phantom-mode signaloperation, the DSLAM 485 can be used to implement phantom-mode signaloperation between lines 491, 492, thus creating a phantom-mode signalchannel 493 between lines 491, 492 in either an upstream or downstreamdirection. The system of FIG. 4B can operate in ways analogous to thesystem of FIG. 4A, as will be appreciated by those skilled in the art,though differences are achievable while still implementing embodimentsof the present invention.

A method 500 according to one or more embodiments of the presentinvention is shown in FIG. 5. At 510 a first communication line isconfigured to operate as a transmission antenna, for example by usingthe apparatus and/or techniques illustrated in FIGS. 3A-3C. At 520 asecond communication line is likewise configured to operate as areception antenna, again possibly implementing apparatus and/ortechniques illustrated in FIGS. 3A-3C. Data is then transmitted on thefirst line's transmission antenna at 530 and is broadcast to the secondcommunication line. At 540 the receiving device on the secondcommunication line, or any other apparatus and/or equipment used toassist in the operation of the second line, identifies the phantom-modesignal data, for example using techniques described above. In someembodiments, the two communication lines can be DSL loops in a commonbinder. These DSL loops may be operated in a one-sided or two-sidedvectored system.

Generally, embodiments of the present invention employ various processesinvolving data stored in or transferred through one or more computersystems, which may be a single computer, multiple computers and/or acombination of computers (any and all of which may be referred tointerchangeably herein as a “computer” and/or a “computer system”).Embodiments of the present invention also relate to a hardware device orother apparatus for performing these operations. This apparatus may bespecially constructed for the required purposes, or it may be ageneral-purpose computer and/or computer system selectively activated orreconfigured by a computer program and/or data structure stored in acomputer. The-processes presented herein are not inherently related toany particular computer or other apparatus. In-particular, variousgeneral-purpose machines may be used with programs written in accordancewith the teachings herein, or it may be more convenient to construct amore specialized apparatus to perform the required method steps. Aparticular structure for a variety of these machines will be apparent tothose of ordinary skill in the art based on the description given below.

Embodiments of the present invention as described above employ variousprocess steps involving data stored in computer systems. These steps arethose requiring physical manipulation of physical quantities. Usually,though not necessarily, these quantities take the form of electrical ormagnetic signals capable of being stored, transferred, combined,compared and otherwise manipulated. It is sometimes convenient,principally for reasons of common usage, to refer to these signals asbits, bitstreams, data signals, control signals, values, elements,variables, characters, data structures or the like. It should beremembered, however, that all of these and similar terms are to beassociated with the appropriate physical quantities and are merelyconvenient labels applied to these quantities.

Further, the manipulations performed are often referred to in terms suchas identifying, fitting or comparing. In any of the operations describedherein that form part of the present invention these operations aremachine operations. Useful machines for performing the operations ofembodiments of the present invention include general purpose digitalcomputers or other similar devices. In all cases, there should be bornein mind the distinction between the method of operations in operating acomputer and the method of computation itself. Embodiments of thepresent invention relate to method steps for operating a computer inprocessing electrical or other physical signals to generate otherdesired physical signals.

Embodiments of the present invention also relate to an apparatus forperforming these operations. This apparatus may be specially constructedfor the required purposes, or it may be a general purpose computerselectively activated or reconfigured by a computer program stored inthe computer. The processes presented herein are not inherently relatedto any particular computer or other apparatus. In particular, variousgeneral purpose machines may be used with programs written in accordancewith the teachings herein, or it may be more convenient to construct amore specialized apparatus to perform the required method steps. Therequired structure for a variety of these machines will appear from thedescription given above.

In addition, embodiments of the present invention further relate tocomputer readable media that include program instructions for performingvarious computer-implemented operations. The media and programinstructions may be those specially designed and constructed for thepurposes of the present invention, or they may be of the kind well knownand available to those having skill in the computer software arts.Examples of computer-readable media include, but are not limited to,magnetic media such as hard disks, floppy disks, and magnetic tape;optical media such as CD-ROM disks; magneto-optical media such asoptical disks; and hardware devices that are specially configured tostore and perform program instructions, such as read-only memory devices(ROM) and random access memory (RAM). Examples of program instructionsinclude both machine code, such as produced by a compiler, and filescontaining higher level code that may be executed by the computer usingan interpreter.

FIG. 6 illustrates a typical computer system that can be used by a userand/or controller in accordance with one or more embodiments of thepresent invention. The computer system 600 includes any number ofprocessors 602 (also referred to as central processing units, or CPUs)that are coupled to storage devices including primary storage 606(typically a random access memory, or RAM), primary storage 604(typically a read only memory, or ROM). As is well known in the art,primary storage 604 acts to transfer data and instructionsuni-directionally to the CPU and primary storage 606 is used typicallyto transfer data and instructions in a bi-directional manner. Both ofthese primary storage devices may include any suitable of thecomputer-readable media described above. A mass storage device 608 alsois coupled bi-directionally to CPU 602 and provides additional datastorage capacity and may include any of the computer-readable mediadescribed above. The mass storage device 608 may be used to storeprograms, data and the like and is typically a secondary storage mediumsuch as a hard disk that is slower than primary storage. It will beappreciated that the information retained within the mass storage device608, may, in appropriate cases, be incorporated in standard fashion aspart of primary storage 606 as virtual memory. A specific mass storagedevice such as a CD-ROM 614 may also pass data uni-directionally to theCPU.

CPU 602 also is coupled to an interface 610 that includes one or moreinput/output devices such as such as video monitors, track balls, mice,keyboards, microphones, touch-sensitive displays, transducer cardreaders, magnetic or paper tape readers, tablets, styluses, voice orhandwriting recognizers, or other well-known input devices such as, ofcourse, other computers. Finally, CPU 602 optionally may be coupled to acomputer or telecommunications network using a network connection asshown generally at 612. With such a network connection, it iscontemplated that the CPU might receive information from the network, ormight output information to the network in the course of performing theabove-described method steps. The above-described devices and materialswill be familiar to those of skill in the computer hardware and softwarearts. The hardware elements described above may define multiple softwaremodules for performing the operations of this invention. For example,instructions for running a codeword composition controller may be storedon mass storage device 608 or 614 and executed on CPU 602 in conjunctionwith primary memory 606. In a preferred embodiment, the controller isdivided into software submodules.

The many features and advantages of the present invention are apparentfrom the written description, and thus, the appended claims are intendedto cover all such features and advantages of the invention. Further,since numerous modifications and changes will readily occur to thoseskilled in the art, the present invention is not limited to the exactconstruction and operation as illustrated and described. Therefore, thedescribed embodiments should be taken as illustrative and notrestrictive, and the invention should not be limited to the detailsgiven herein but should be defined by the following claims and theirfull scope of equivalents, whether foreseeable or unforeseeable now orin the future.

1. A Digital Subscriber Line (DSL) communication system comprising: afirst DSL loop and a second DSL loop each having a transformer centertap at one end; an excitation voltage generator for each of the firstand second DSL loops, the excitation voltage generators to connect thetransformer center taps of the first and second DSL loops to a commonground; a third DSL loop and a fourth DSL loop each having a transformercenter tap at one end; a load impedance for each of the third and fourthDSL loops, the load impedances to connect the transformer center taps ofthe third and fourth DSL loops to the common ground; and wherein datasignals created by the excitation voltage generators transmitted on thefirst and the second DSL loops generate data signals on the third andforth DSL loops which are applied to the load impedances.
 2. The DSLcommunication system of claim 1, wherein the first, second, third, andfourth DSL loops operate within a vectored DSL communication system. 3.The DSL communication system of claim 2, wherein the vectored DSLcommunication system comprises the first, second, third, and fourth DSLloops within a vectored binder of DSL loops, and wherein the vectoredDSL communication system to superimpose phantom-mode signals onto thefirst, second, third, and fourth DSL loops within the vectored binder ofDSL loops to expand extra transmission modes.
 4. The DSL communicationsystem of claim 2: wherein the vectored DSL communication systemcomprises the first and second DSL loops designated as a first pair andthe third and fourth DSL loops designated as a second pair, and whereineach pair is treated as a common-mode antenna with respect to earthground via the common ground; and wherein the excitation voltagegenerators to selectively excite signals at the first pair via thetransformer center taps at the one end of each respective DSL loop inthe first pair, wherein the one end of each respective DSL loop in thefirst pair comprises a transmit end with respect to the common ground.5. The DSL communication system of claim 4, further comprising: acorresponding receiver on the non-excited second pair to sense thesignals between their transformer center taps and the common ground atthe opposite ends of each respective DSL loop in the second pair.
 6. TheDSL communication system of claim 1, wherein the first DSL loop and thesecond DSL loop are controlled by at least one of the following: acontrolling computer; a controller; and a DSL optimizer.
 7. The DSLcommunication system of claim 1, further comprising: a transformercenter tap at a second end of the first DSL loop coupled to a first opencircuit; a transformer center tap at a second end of the second DSL loopcoupled to a second open circuit; a transformer center tap at a secondend of the third DSL loop coupled to a third open circuit; and atransformer center tap at a second end of the fourth DSL loop coupled toa fourth open circuit.
 8. The DSL communication system of claim 7:wherein the first DSL loop first end is an upstream end of the first DSLloop, wherein the second DSL loop first end is an upstream end of thesecond DSL loop, wherein the third DSL loop first end is an upstream endof the third DSL loop, and wherein the fourth DSL loop first end is anupstream end of the fourth DSL loop; and further wherein the first DSLloop first end is a downstream end of the first DSL loop, wherein thesecond DSL loop first end is a downstream end of the second DSL loop,wherein the third DSL loop first end is a downstream end of the thirdDSL loop, and wherein the fourth DSL loop first end is a downstream endof the fourth DSL loop.
 9. The DSL communication system of claim 7:wherein the first DSL loop and the second DSL loop each further comprisea hybrid circuit at the first end of each respective loop; wherein thethird DSL loop and the fourth DSL loop each further comprises a hybridcircuit at the second end of each respective loop; and further whereinthe first, second, third, and fourth DSL loops are configured to operatebi-directionally sending phantom-mode signals that expand extratransmission modes of the DSL communication system.
 10. A methodcomprising: transmitting data signals on a first DSL loop and a secondDSL loop each having a transformer center tap at one end, each of thefirst and second DSL loops coupled with an excitation voltage generatorvia the transformer center tap of each of the first DSL loop and thesecond DSL loop, wherein each of the excitation voltage generatorsconnects the transformer center taps of the first and second DSL loopsto a common ground; applying, via the excitation voltage generators, anexcitation voltage to each of the first and second DSL loops; receivingthe data signals on a third DSL loop and a fourth DSL loop through thecommon ground, the third and fourth DSL loops each having a transformercenter tap at one end and each connected to the common ground via a loadimpedance connecting the transformer center tap at the one end of eachof the third DSL loop and the fourth DSL loop to the common ground; andapplying, via the load impedances, the excitation voltage to the datasignal received on the third DSL loop and the fourth DSL loop.
 11. Themethod of claim 10, wherein the excitation voltage applied to each ofthe first and second DSL loops generates the data signals received onthe third and fourth DSL loops.
 12. The method of claim 10, wherein themethod is performed within a vectored DSL communication system; andwherein the method further comprises applying vectoring to the first,second, third, and fourth DSL loops within the vectored DSLcommunication system.
 13. The method of claim 10: wherein the first,second, third, and fourth DSL loops exist within a vectored binder ofDSL loops; and wherein applying the excitation voltage to each of thefirst and second DSL loops comprises superimposing signals onto thefirst, second, third, and fourth DSL loops within the vectored binder ofDSL loops to expand extra transmission modes.
 14. The method of claim13: designating the first and second DSL loops as a first pair and thethird and fourth DSL loops as a second pair; treating each pair as acommon-mode antenna with respect to earth ground via the common ground;and selectively exciting signals, via the excitation voltage generatorscoupled with the first pair, at each DSL loop in the first pair via thetransformer center taps of the first pair.
 15. The method of claim 14:sensing, via a corresponding receiver coupled with the non-excitedsecond pair, signals resulting from selectively exciting the first pair,the signals sensed on the non-excited second pair between thetransformer center taps of the non-excited second pair and the commonground at the opposite ends of each respective DSL loop in thenon-excited second pair.
 16. The method of claim 10, wherein the first,second, third, and fourth DSL loops are each controlled by a controller.17. A controller having a data module for collecting operational datafrom a Digital Subscriber Line (DSL) communication system comprising: afirst DSL loop and a second DSL loop each having a transformer centertap at one end; an excitation voltage generator for each of the firstand second DSL loops, the excitation voltage generators to connect thetransformer center taps of the first and second DSL loops to a commonground; a third DSL loop and a fourth DSL loop each having a transformercenter tap at one end; a load impedance for each of the third and fourthDSL loops, the load impedances to connect the transformer center taps ofthe third and fourth DSL loops to the common ground; a Dynamic SpectrumManager (DSM) server communicatively interfaced with the data module,wherein the DSM server to analyze the operational data collected fromthe DSL communication system; and an instruction generator to instructthe first and second DSL loops and the third and fourth DSL loops totransmit data signals between the first and second DSL loops and thethird and fourth DSL loops.
 18. The controller of claim 17, wherein thecontroller comprises a DSL optimizer.
 19. The controller of claim 17,wherein the controller further comprises: means for collecting theoperational data from the DSL communication system; means for analyzingthe operational data collected by the collecting means; and wherein theinstruction generator comprises means for generating instructions tocontrol the first, second, third, and fourth DSL loops, wherein themeans for generating instructions are to assist the first and second DSLloops in transmitting data as a data signal, and further wherein thegenerated instructions are to assist the third and fourth DSL loops inreceiving the transmitted data as the data signal.
 20. The controller ofclaim 17, wherein the generated instructions comprise at leastinstructions causing the excitation voltage generators coupled with thefirst and second DSL loops to apply an excitation voltage to the firstand second DSL loops.